羰基镍的物理性质.docx

http// 65 kPa at 30 C. Nickel tetracarbonyl is virtually insoluble in water, but soluble in many organic solvents. It does not react with dilute mineral acids. It is thermally unstable, decomposing to nickel and carbon monoxide. It burns in air with a luminous flame, giving nickel oxide and carbon dioxide, and s explosive mixtures with air 3 – 34 vol Ni CO4 . The molecule is tetrahedral, with linear Ni–C–O bonding.p-bond and sbonds. The bonding consists of both a Ni–C Production . Nickel tetracarbonyl is ed by direct reaction of carbon monoxide and finely divided nickel at relatively low temperatures [8] NiNig 4 COg CO4g At atmospheric pressure, the maximum rate of ation of nickel tetracarbonyl is at 130 C for pure nickel. The temperature at which the rate of ation is a maximum decreases in the presence of a catalyst such as sulfur, and increases with pressure. The reverse reaction begins above ca. 180 C. This reversible reaction is the basis of the atmospheric-pressure Mond process and the INCO pressure process for the production of high-purity nickel Nickel - 6.3. Carbonyl Refining . Nickel tetracarbonyl canpellet and powder also be prepared in solution by a variety of s [9]. Users of nickel tetracarbonyl frequently produce their own supply, but it is commercially available in the United States. The conditions under which nickel tetracarbonyl is ed are important because of the possibility of corrosion or transfer of nickel within a system, and in view of its high toxicity. The mere coexistence of carbon monoxide and nickel in some does not mean that nickel tetracarbonyl will . Other criteria must be met 1 a fully reduced nickel-containing surface, 2 a reducing gas containing carbon monoxide, 3 the ation must be thermodynamically possible, which generally means low temperature ambient to 150 C and high carbon monoxide partial pressures. In addition, the presence of a catalyst such as sulfur accelerates nickel tetracarbonyl ation. One situation where a significant amount of nickel tetracarbonyl can is from a finely divided reduced nickel catalyst and carbon monoxide at low temperature. This is well known to users of nickel catalysts, and such conditions are avoided. Other than this, it is rare that significant amounts of nickel tetracarbonyl are ed. Environmentally, precautions preventing contamination of the workplace by the carbon monoxide will also prevent contamination by any nickel tetracarbonyl. The presence of nickel tetracarbonyl has been suggested but not demonstrated in cigarette smoke and in gases from the combustion of fossil fuels containing nickel. Attempts to detect it in welding fume failed [10]. Uses . Apart from being an intermediate in the carbonyl refining of nickel, nickel tetracarbonyl can be thermally decomposed to nickel plate other materials, for example, in mold production or in a fluidized bed. It is also used as a carbonylating agent or catalyst in organic chemistry. Analysis . Nickel tetracarbonyl can be analyzed by decomposition and conventional analysis of the nickel, by gas chromatography, UV or IR spectroscopy. There is a highly sensitive based on the chemiluminescent reaction of nickel tetracarbonyl with ozone [11]. Commercial instruments based on infrared or chemiluminescent analysis are available. Reactions of Nickel Tetracarbonyl Nickel tetracarbonyl undergoes oxidation, reduction, and substitution reactions [12] , [13]. These are normally carried out in organic solvents below ca. 50 C to prevent thermal decomposition of the nickel tetracarbonyl. Reaction with various oxidizing agents gives Ni II compounds. Concentrated nitric acid gives nickel nitrate. Solutions of nickel tetracarbonyl in organic solvents are oxidized by air to basic nickel carbonate and by halogens to the corresponding nickel dihalide. Decomposition of nickel tetracarbonyl with bromine water is useful as a means of disposal or for analysis. Reduction reactions, generally with alkali metals, give polynuclear anions ulated as [ Ni2CO6]2– , [ Ni3CO8]2– , [ Ni4CO9]2– , [ Ni5CO9]2– , and [ Ni6CO12]2–. Reduction of nickel tetracarbonyl by alkali metals in liquid ammonia gives a carbonyl hydride [NiHCO3]2 , isolated as a tetra-ammoniate. Interest in substitution compounds of nickel tetracarbonyl blossomed following the publication in 1948 of work by REPPE and coworkers showing that an effective class of catalysts for the trimerization of acetylene compounds could be ed by substituting CO groups in Ni CO4 by donor ligands such as triphenylphosphine. Thousands of substitution compounds of nickel tetracarbonyl have now been prepared. Most are with ligands containing the group 15 elements phosphorus, arsenic, or antimony as electron donor, but carbon, nitrogen, and unsaturated organic molecules can also serve as ligands. Some of the simpler substitution compounds with phosphorus ligands are Ni COnPX3 4–n , n 0 – 3, X H, F, Cl, CH3 , C2H5 , C6H5substituted phosphines and X OCH3 , OC2H5 , OC6H5 phosphites. The degree of substitution is controlled by steric and electronic effects. For example, with PF3 and PC6H5 3 , only mono- and disubstituted compounds are ed, whereas with PCl3 and POC6H5 3 the carbon monoxide molecules can be completely replaced. The tetrakisligand compounds Ni PF3 4 and Ni [PC6H5 3]4 can be prepared by other means. 2 , and NiLSubstitution by chelating ligands is also possible, e.g., CO2NiL o-C6H4-[PC2H5 2]2.where L Fewer substitution compounds based on arsenic and antimony have been prepared. Examples include Ni CO3AsX3 X CH3 , C2H5, C6H5 , OCH3, OC2H5 , OC6H5 and Ni CO3SbX3 X Cl, C2H5 , C6H5 , OC6H5. [8]Y. Monteil, P. Raffin, J. Bouix, Thermochim. Acta 125 1988 327 – 346. [9]F. Boix et al., Synth. Commun. 17 1987 1149 – 1153. [10]L. G. Wiseman, Weld. J. Miami 68 1989 192 – 197. [11]P. M. Houpt, A. Van der Waal, F. Langeweg, Anal. Chim. Acta. 136 1982 421 – 424. [12]P. W. Jolly, G. Wilke The Organic Chemistry of Nickel, vol. 1, Academic Press, New York 1974. [13]P. W. Jolly in G. Wilkinson, F. G. A. Stone, E. W. Abel eds. Comprehensive Organometallic Chemistry, vol. 6, Pergamon Press, Oxford 1982, pp. 1 – 36.